Parasite
by KarmicRetribution
Summary: What if, Frisk is a parasite, hopping from timeline to timeline, looking for an ideal timeline to take over. Unlike Chara, who takes over Genocide Runs, Frisk takes over Pacifist Runs. And not even Sans knows. A reader self-insert AU. (Rated T for maybe some triggering and definitely stressful content.)


**Author's note: Thanks to JenniferMarie20 for helping me edit this! If you haven't heard of them, go check them out 'cause they are a super duper awesome writer! And the real question that we all asked ourselves (or at least I did) that I answered in this story is,**

 **Who is the real parasite?**

I finally made it. All the deaths.

All the resets. Each time where I thought I had drawn my last breath, or where I thought I had no other choice but to kill, I managed to find a different way, a better way. That indescribable force of will that was called DETERMINATION that carried me through, and brought me back from the brink of death over and over and over and over again. I had made so many wonderful friends, and managed to break the barrier as well. It was finally over. I had finally gotten everyone a happy ending. And it was all going to be taken away from me.

* * *

I awoke on top of golden flowers and with the light of a far off hole blinding my eyes. I rubbed my aching head. Ugh, I'm never going hiking again. Fortunately, there didn't seem to be any noticeable injuries on my body.

With a jolt I sat up. For one heart-stopping second, I couldn't remember my name. Frantically casting about my memories for that vital piece of my identity, I sighed in relief as it came back to me. [Y/N]. My name was [Y/N].

I collapsed back down onto the flowers and took stock of my situation. I had gone hiking, despite the stories that surrounded this particular mountain. Many of my friends had said to go farther away to find a less dangerous mountain. Determined to climb this mountain, I had called them superstitious and went anyway. Apparently when I tripped I had fallen down that hole, and somehow miraculously survived that fall without even a broken bone. Now I just needed to find a way to get help or get out. Despite being only [Y/A] years old, I was very independent, which was part of the reason I had gone mountain climbing alone, so I had a day at least before my friends decided to call the authorities, and wouldn't that be embarrassing if I proved them right.

Well, there was no time like the present. Grunting, I stood up and stumbled down a tunnel, the light of the outside world disappearing behind me.

* * *

My journey had started off with Flowey attempting to trick and kill me. Then Toriel saving me. Unable to kill anyone, to take away the life of another even if they were going to kill me, I decided to trust her, and try to escape if she betrayed me.

Wandering through the Ruins I learned a lot about how the Underground worked. Despite constantly running into monsters, I always somehow avoided getting killed and managed to spare them. Toriel took me into her home and made me feel welcome with butterscotch-cinnamon pie. But when I tried to leave she turned hostile, frightening me and making me more determined to leave.

When she forced me to fight, I thought she had back-stabbed me like Flowey, but even then I couldn't fight her, knowing I might have to kill her, and something prevented me from fleeing. I just had the feeling I couldn't run from this. I did the best I could with just sparing, believing at any second I was going to die. But against all hope she eventually spared me in turn, and let me go.

I met Flowey again outside the doorway Toriel tried to destroy. He taunted me, mocking me about my inability to kill Toriel, and then claiming that I will die over and over again, and be forced to kill in order to avoid being killed myself. Or, I would give up, and let him have control over the Underground again. With those chilling words hanging over my head, he left. I was always called stubborn, doing things out of spite to prove people wrong, or just because others couldn't or wouldn't. People have called me crazy, or insane, or even brave. Whatever it was, I was determined to prove Flowey wrong.

Leaving the Ruins I was still apprehensive, and a little saddened by Toriel completely abandoning me. Independent or not, that stung. Then I met the enigmatic Sans, who managed to make me laugh from the beginning, in the face of what seemed like a lost cause, and Papyrus, Sans' energetic brother whose puzzles helped take my mind off of the serious matters that weighed me down.

From that encounter on, I was determined to make sure I did my best to be the best possible person that I could be, just for the kindness Papyrus showed me in our battles. I had lightly flirted with him, mostly to make him flustered. He said he was a skeleton with very high standards. I said the first thing that came to mind, _I can make spaghetti!_ But even as I said it I thought I felt ' _I have zero redeeming qualities_ ' in the back of my mind. In the end I actually went on a date with him. It was… weird. But Papyrus never let me die, and went out of his way for me, which was something I could never forget. Beforehand I only did what I had to to survive. After Papyrus I did what I had to to make everyone happy as well.

* * *

I fought Undyne fiercely. I cooked even more fiercely with Undyne. I befriended Undyne using all my might.

I bought a ton of hotdogs and hotcats from Sans. I let him balance them on my head when I no longer had any room to carry them. They were surprisingly stackable. I wondered at the snow that covered his station even in Hotland. I ate at Grillby's with him and laughed at all his jokes.

I laid among the echo flowers and listened to the stories they told of the lives of the monsters that came there. I watched as Flowey shadowed my every step.

I petted the dogs of Snowdin to satisfaction. I comforted the Abandoned Quiche. I wore the many accessories I found littered about. I danced with spiders and dodged muffin monsters.

I helped Alphys overcome her fears and I help Undyne set her and Alphys up on a date. I went to the secret lab. I was fearful of the amalgamates I met there. Then I became friends with them.

I faced Asgore down and beat him. I fought him when I had fought no monster before. He had given me no other choice.

…

And I died. I died so many times, to so many people. I was killed over and over again when facing Mettaton. When facing Undyne. When facing Muffet. And even when facing the weakest of monsters because I was too slow, I did not have enough energy, I was just tired of it all. But I kept coming back. I kept trying. I ended up fleeing a lot. I ended up coming back because of that promise I made to myself for Papyrus to give everyone a happy ending. And I died some more, but in the end I was always able to win.

...

I forgave and spared Asgore in the end. I watched as it was all for naught when Flowey killed him and took the souls. I fought Flowey, and the souls beat him.

I reset out of guilt for the lost life of the king. I ran away before I could fight him. Then I came back, determined to do something different. And I was the one who was saved. By all my friends and all the monsters in the Underground.

And Flowey took them. Revealing himself as the dead prince. Called out to me and claimed he was my best friend. And he became set on beating me.

* * *

Leading to now.

 _Can't move your body._

To where I would bet to all the deities in the world that this is where it would end.

 _Nothing happened._

Asriel Dreemurr struck me down.

 _You struggle..._

Landed the killing blow.

 _Nothing happened._

But I couldn't die and give him power.

 _You tried to reach your SAVE file._

He would just abuse it again and again.

 _Nothing happened._

He would make all my friends suffer.

 _You tried again to reach your SAVE file._

 _Nothing happened._

And what he said at the beginning was still stuck in my mind.

 _Seems saving the game really is impossible._

So I refused.

 _..._

 _But..._

 _Maybe, with what little power you have..._

 _You can SAVE something else._

 _You reached out to ASRIEL's SOUL and called out to your friends._

 _They're in there somewhere, aren't they?_

 _..._

 _Within the depths of ASRIEL's SOUL, something's resonating..!_

 _The Lost Soul appeared._

* * *

 _Suddenly, the memories are flooding back!_

* * *

I could feel my friend's souls resonating within Asriel.

I called out to them and helped bring them back to themselves using what I had learned through my journey.

Again and again I saved my friends and then I came to the last person needed to be saved. Him.

You feel something strongly resonating within ASRIEL.

I called out to him, and he called back to me. And I saved him.

* * *

I felt my legs shake, threatening to collapse under me. I was very tempted to do so, but I couldn't. Not just yet. I felt relieved tears rush to my eyes, as I realized it was all over. A sob hitched in my throat, but I refused to let it out. My body ached with the accumulated bruises and injuries from our fight. I rushed towards Asriel, and he looked at me.

As relief flooded your SOUL, another feeling followed. You felt… DETERMINED? No, _you_ weren't DETERMINED. That little voice inside your head, the one that guided you and had kept you DETERMINED throughout your ordeals, _they_ were DETERMINED. And between one moment and the next… you were no longer in control.

Asriel asked you for your name, and your mouth said, 'Frisk.' With a smile that to you felt smug, 'My name is Frisk.'

Shock paralyzed you for a second before you realized what just happened. Mental tears started streaming down your face as you screamed No! And threw yourself at the mental barrier that had been put up. You pounded it as you desperately insisted that _that_ wasn't your name, your name was [Y/N]. Your name was [Y/N]!

Your body forgave Asriel and gave him a hug, just as you would have, but it _wasn't_ you. That wasn't you there!

Everyone woke up with the Barrier broken, and they thanked you and claimed that you were their savior. What a joke. They were thanking a SOULess husk. How come no one noticed something was wrong?!

* * *

Eventually, your voice grew hoarse, and your attempts became more feeble. You watched as Frisk lived out your life on the Surface, in the company of the Monsters. Toriel tucked Frisk in every night. Asgore gave them piggy back rides on their shoulders. Alphys and Undyne binge watched anime with Frisk. And Papyrus fed them his spaghetti.

They led the perfect life, in the care of those that loved them and had grown to love them from their time in the Underground. And it was all a lie.

They walked around in your skin like some sort of sick costume. You eventually took to passing long periods of time in a corner of your mind. There you had met another child that was also trapped in here. Their name was Chara. They were terrible frightened of Frisk, and refused to tell you anything about them. Instead you kept each other company with tales from when you were alive. Because for all intents and purposes, you were also dead.

* * *

They told you about when they were the beloved adopted child of the Queen and King of the Monsters, and you told them about your friends.

About how one of them was so brave they could watch horror movies with you and not be afraid afterwards, while you had to sleep with the light on. Another was so nice they would make you food when you felt sad, while another would tell you to push on through it. One of them was such an activist, they got so worked up over the unfairness of others. They once made you stand outside for a night for a protest that was for equal rights. Of your friends only one of them was able to patiently last the whole night. Your bestest friend stood by her principles no matter what. As a joke you called them self righteous but you admired their integrity. Thinking about your friends both cheered you up and made you sadder as you realized you would never see them again.

One time, weary from all that has happened, you attempted to reach out to Frisk, and you simply asked, _Why? Why do this to you?_

That they responded at all surprised you. They said, _Because I_ _can_ _. Because in this timeline you actually managed to make everything go right. And that is exactly what I have been looking for._

 _In my world it's take or be taken from. And guess what [Y/N]? I took your Happy Ending from you. Thanks for Staying DETERMINED for me. =)_

 **Author's note: Ok guys, I went out on a limb a bit with this story, with a different way of writing than I am usually comfortable with, so any feedback would be nice. This is just a short story and I'm sorry, but this is the end. Please leave a Fave, Follow, or Review. Definitely the last one. Feedback is what artist's live on. We thrive on it. Without it, we whither away. Just saying. If you read a story, always leave a comment if you liked it, even if you just say that you liked it. This applies to all writers. It makes us happy! ^u^**


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